Beirut: A senior Syrian opposition official on Friday ruled out even indirect peace talks with the government before a halt to Russian air strikes and the lifting of government blockades on populated areas.

U.S. Secretary of State John Kerry on Thursday insisted peace talks would go ahead in Geneva next week but they would not be face-to-face. The Syrian government, which is backed by Russia, has said it is ready to attend.

But George Sabra, deputy head of the opposition delegation, said obstacles which the opposition say are obstructing the talks had not been removed. "There must be a halt to the bombardment of civilians by Russian planes, and sieges of blockaded areas must be lifted," Sabra said by telephone.

"The form of the talks does not concern us, but the conditions must be appropriate for the negotiations," Sabra told Reuters. Asked if that meant the opposition would not attend the kind of indirect talks mentioned by Kerry, he said "yes".

Riad Hijab, who chairs the opposition council, was due to discuss diplomatic efforts with U.S. Secretary of State John Kerry on Saturday and "all the matters will be tabled clearly", Sabra said.

The talks have also been thrown into doubt by a disagreement over who should represent the opposition. Russia wants the opposition delegation expanded to include groups such a Kurdish faction that controls wide areas of the northeast.

Sabra`s opposition council, the High Negotiations Committee (HNC), was formed in Saudi Arabia last month and groups political and armed opponents of President Bashar al-Assad, including major rebel factions fighting Damascus in western Syria.